Hitherto, asbestos has been used as a reinforcement in inorganic board, but the environmental pollution caused by the scattering of fine asbestos powder has become a serious problem, so that at present, woody reinforcements such as wood flake, wood fiber and the like are being used instead of asbestos. Nevertheless, there is a problem in that inorganic board using such materials for woody reinforcement has poor dimensional stability, so that when said inorganic board absorbs or discharges moisture, said inorganic board elongates or contracts, resulting in the warping, and further, cracking of said inorganic board.
To solve said problem, an idea wherein mica is added to the mixture of woody reinforcements and cement is proposed. Mica has a high elasticity, so that dimensional stability, cutting workability, nailing workability and the like are much improved by the added mica content in said inorganic board (See, for example, Patent literatures 1, 2, and 3).
References Cited 1:
Published unexamined Japanese Patent Application 2002-166406
References Cited 2:
Published unexamined Japanese Patent Application Heisei 06-329457
References Cited 3:
Published unexamined Japanese Patent Application Heisei 05-124845